- Remove unused TaskStatusResponse import from memory_api_schema
- Add _sanitize_task_result() helper function to convert non-serializable types (UUID, datetime) to strings
- Update get_write_task_status endpoint to use sanitization instead of TaskStatusResponse validation
- Update get_read_task_status endpoint to use sanitization instead of TaskStatusResponse validation
- Ensures Celery task results are properly JSON-serializable before returning to clients